Devices for feeding fluid under pressure to at least two load circuits

ABSTRACT

In a device for feeding fluid under pressure to at least two load circuits, of which one has priority, the power required to drive a group of constant flow pumps connected to the priority load circuit is subtracted from the power of the motor driving this group of pumps and a second group of variable flow pumps connected to the non-priority load, the difference in the powers being used for the second group of variable flow pumps, the subtraction being effected by a valve coupled in a pipe connecting the delivery pipe from the constant flow group of pumps and an inlet chamber of a regulator of the group of variable flow pumps, the valve providing a variable fluid constriction which is varied in dependence on the pressure in the delivery pipe of the group of variable flow pumps.

1451 July 29,1975

3,575,000 4/1971 l-lufeld...........................60/422 3,767,327 10/1973 Wagenseil.........................

[ DEVICES FOR FEEDING FLUID UNDER PRESSURE TO AT LEAST TWO LOAD CIRCUITS Primary Examiner-Wi1liam L. Freeh [75] Inventors: Michel F. Capelle; Claude Pinson, Assistant g p Lapoime Attorney, Agent, or Firm-Fitzpatrick, Cella, Harper & Scinto both of Senlis, France [73] Assignee: Societe Anonyme: Poclain, Oise,

France [57] ABSTRACT In a device for feeding fluid under pressure to at least [22] Filed: Apr. 29, 1974 PP 464,340 two load circuits, of which one has priority, the power required to drive a group of constant flow pumps con- [30] Foreign Application p i i Dam nected to the priority load circuit is subtracted from May 28, 1973 the power of the motor driving this group of pumps and a second group of variable flow pumps connected to the non-priority load, the difference in the powers France.............................. 73.19331 being used for the second group of variable flow pumps, the subtraction being effected by a valve coupled in a pipe connecting the delivery pipe from the constant flow group of pumps and an inlet chamber of 80 6 2 M94 8 24 1 4 2 M n .64 6 6 .13 2D/ W6 11 4Fm mmh c r. Na e NS L l d Std UI .F HUN 555 a regulator of the group of variable flow pumps, the

[56] References Cited UNITED STATES PATENTS valve providing a variable fluid constriction which is varied in dependence on the pressure in the delivery pipe of the group of variable flow pumps.

60/421 Malott. 60/422 Stremple..............................r 60/422 5 ClalmS, 2 Drawing gur s 2,316,926 4/1943 Willett........................ 3,355,994 12/1967 3,561,327 2/1971 PATENTED JUL 2 91975 SHEET DEVICES FOR FEEDING FLUID UNDER PRESSURE TO AT LEAST TWO LOAD CIRCUITS The present invention relates to improvements in devices for feeding fluid under pressure to at least two load circuits.

Devices are already known for feeding fluid under pressure, of which the single motor for driving various pumps has a maximum power less than the sum of the maximum powers of the pumps.

it can happen in the simplest case that one of the pumps has a constant flow and feeds a circuit which is considered to have priority, another of the pumps being variable-flow and feeding another circuit which does not have priority.

A device must be conceived, for use in the case in which the sum of the powers necessary at a given moment for driving these two pumps in greater than the maximum power of the motor, which enables driving of the constant-flow pump with the required power, and hence the feeding of the priority circuit to be continued, and automatically limits the driving power to the variable-flow pump so that the total power necessary for the driving of the pumps remains less than or at most equal to the maximum power of the motor.

According to the present invention there is provided a device for feeding fluid under pressure to at least two load circuits, comprising:

two groups of pumps for feeding fluid to a respective one of said load circuits and each including a pump, a driving shaft and a delivery pipe, one of said groups of pumps being constant-flow, and the other of said groups of pumps being variable-flow,

driving motor means having a single output shaft to which are coupled the driving shaft of said pumps,

power regulator means including a body and an element movable with respect to the body and which is coupled between the flow control means and the body of said variable-flow group of pumps, said regulator including ram means interposed between said body and said movable element of said regulator and comprising an inlet chamber,

pipe means connecting the delivery pipe from said constant flow group of pumps to said inlet chamber,

and

a valve arranged in said connecting pipe means and comprising a body, a slide movably mounted in said body, an inlet connected to said delivery pipe by said connecting pipe means, two outlets of which a first outlet is connected to a fluid tank and the second outlet is connected to said inlet chamber of said rarn means by said connecting pipe means, a fluid connection for control of the position of said slide, said fluid connection being connected to the delivery pipe of said variableflow group of pumps, and a passage between said body and said slide of said valve at least one of the dimensions of which varies as a function of the position of the said slide in said body, said inlet, said first outlet and said second outlet being in permanent communications with said passage, said second outlet communicating with said passage at a region intermediate communication of said inlet and said first outlet with said passage, and the portion of said passage lying between the regions of communication of said inlet and said second outlet with said passage forming a variable fluid constriction.

Advantageously the device includes a calibrated valve arranged in said connecting pipe means between said valve and the connection of said connecting pipe means to said delivery pipe of said constant-flow group of pumps, to be piloted by the pressure of fluid in said delivery pipe.

Preferably the slide is mounted to slide in said body of said valve, is coupled to the movable member of a ram assembly, and is subjected to the effect of the pressure of the control fluid and the opposing action of a return member coupled between said slide and said body of said valve.

Advantageously said passage is defined by a groove in the outer face of said slide of said valve and a channel in said slide and connecting said groove with a recess in said body of said valve which is connected to said second outlet from said valve, said groove being permanently connected to said inlet and said first outlet, the value of said variable constriction being proportional to the distance separating the regions of communication of said first and second outlets with the passage.

The power regulator may include a second ram assembly which is interposed between its body and movable element and comprises an inlet chamber connected to said delivery pipe of said variable-flow group of pumps, a return member being interposed between said body and said movable element of said regulator and having an effect opposed to that of fluid when contained in the inlet chamber of the first ram assembly.

The invention will be better understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic view of an embodiment of a feeding device in accordance with the invention, showing part thereof in section; and

FIG. 2 is a graph illustrating the functioning of the feeding device of FIG. 1.

The device illustrated comprises a constant-flow pump 1 and a variable-flow pump 2, which are driven in rotation by a single motor 3 of diesel type. In order to do this, the respective driving shafts 4 and 5 of the two pumps 1 and 2 are each furnished with a pinion 6, 7 which is angularly fast therewith, the two pinions 6 and 7 meshing with one another. In addition, the output shaft 8 of the motor 3 is coupled in rotation to the driving shaft 5 of the variable-flow pump 2 by a known coupling 9.

It should be made clear that the maximum power of the motor 3 is less than the sum of the maximum powers necessary for driving the pumps 1 and 2. It is precisely in order to enable satisfactory operation, while using a motor 3 of only relatively limited power, that the feeding device which will now be described has been devised.

The variable-flow pump 2 is of a known type, for example, of the type with axial pistons arranged in a manner similar to a barrel, and furnished with a member for controlling its flow, which is indicated diagrammatically by a rod 11 mounted to pivot about point 12 and which in the assembly of an axial piston pump consists of a tiltable plate. The pump 2 has its delivery pipe 13 connected to a load circuit 14 and is connected to a fluid tank 15 by its suction pipe 10.

A power regulator 16 comprises a regulator body 17, which is fixed to the body of the pump 2, and a movable element which, in this instance, consists of a rod 18 which is mounted to slide in the body 17 and which is coupled to the rod 11. In known manner, a piston 19 is fast with the rod 18 and is mounted to slide in the bore of a cylinder 20. The piston 19 with the body 17 of the regulator defines two chambers 21 and 23. Chamber 21 is connected by a pipe 22 to the delivery pipe 13 of the variable-flow pump 2, and chamber 23 is connected to atmosphere (or possibly to the fluid tank under zero pressure) by a channel 24. A number of springs 25 of different stiffnesses and lengths are arranged in chamber 23 and are interposed between the piston 19 and the body 17 to have an effect opposing that of fluid in the chamber 21.

Again in known manner, the combination of these springs 25 and the ram assembly, constituted by the piston 19 and the cylinder 20, enables a substantially hyperbolic variation of the flow Q, from the variable-flow pump 2 as a function of the delivery pressure P, from this pump, equal to the pressure of the fluid contained in the pipe 13 or the chamber 21, to be obtained. Substantially one has:

P, XQ,.=constant=W each of the curves C, C in FIG. 2 corresponds with such a constant product which, as is known, is equal to the driving power W, of the pump 2.

The constant flow pump 1 is connected by its suction pipe 26 to the fluid tank 15 and by its delivery pipe 27 to a load circuit 28.

A valve 29 to be called a power subtraction valve (which designation will be understood later) is included in the feeding device. The valve 29 consists of a valve body 30 inside which a slide 31 is mounted to slide with respect to the body 30 and with respect to a member 32 fixed relative to the body 30. A bore 33 is provided in the slide 31 in which the member 32 is received, the slide 31 sealing against the member 32. The member 32 and slide 31 together constitute a ram assembly which includes a chamber 34. This chamber 34 is bounded by the member 32 and the wall of bore 33 and is connected to the outside of the body 30 by a duct 35 in the member 32. The duct 35 is connected to the delivery pipe 13 of the variable-flow pump 2 by a pipe 36. In addition, a spring 37 is interposed between the body 30 of the regulator and the slide 31 and has an effect which is opposed to that of the pressure of fluid in the chamber 34. The spring 37 is housed in a chamber 38 which is in return communication with the tank 15 through a leakage return pipe 39 connected to a first outlet aperture 53 in the body 30.

The valve body 30 is provided with an inlet aperture 40 and a second outlet orifice 41 which are in permanent communication with one another by means of a channel 42 extending transversely in the slide 31, a groove 43 provided in the periphery of the slide and into which the inlet aperture 40 and the first outlet aperture 53 open permanently, and a recess 44 which is arranged in the body 30 and into which the channel 42 and the outlet aperture 41 open permanently. L is the distance separating the transverse planes through the apertures 40 and 53, L is the distance separating the transverse planes through the channel 42 and the inlet aperture 40 and 1 L,,L) is the distance separating the transverse planes through the first outlet orifice 53 and the channel 42. it will be appreciated that the distance L (and therefore the distance I) is variable as a function of the pressure in the chamber 34 and of the stiffness of the spring 37. The portion of the groove 43 of length L constitutes a constriction of variable value which is inversely proportional to the pressure in the chamber 34, interposed between the inlet aperture 40 and the outlet aperture 41, and the pressure in the channel 42 is in turn proportional to the distance I.

A second piston 45 is fast with the rod 18 of the power regulator 16 and is mounted to slide in a cylinder 46 fast with the body 17 of this regulator. The piston 45 defines two chambers 47, 49. Chamber 47 is connected to atmosphere through a duct 48, and chamber 49 is connected to the outlet aperture 41 of the valve 29 by a pipe 50.

A pipe 51 connects the delivery pipe 27 of the constant-flow pump 1 to the inlet aperture 40 of the valve 29. A calibrated valve 52 is arranged in the pipe 51 and is piloted in a known manner by the pressure of fluid in the delivery pipe 27 (or in the portion of the pipe 51 between the delivery pipe 27 and the calibrated valve 52). The calibration pressure of the valve 52 will be made clear later.

The functioning of the feeding device will now be set down. Let there be designated by:

W the maximum power of the motor 3, W, ,P, ,Q, the power, the pressure, and the flow of the variable flow pump 2, W P Q the maximum power, the pressure and the flow of the constant flow pump 1.

ln known manner one has:

( p) m B e (4) The inequality (3) indicates that the power of the motor 3 is greater than the sum ofthe powers necessary for driving the pumps 1 and 2. In that case there is clearly no problem of regulation.

On the other hand the double inequality (4) indicates that the power of the motor 3 may be sufficient for driving solely the constant-flow pump 1 but is insufficient for driving the two pumps 1 and 2 togetherv Now, assuming that the circuit 28 connected to the constantflow pump 1 must be driven as a priority, and consequently the pump 1 must be driven at power W it is absolutely necessary to accept driving the variable-flow pump 2 at only a reduced power W,,,:

Naturally, if the power W, of the motor 3 is greater than the power W, for driving the variable-flow pump 2 it is sensible to start by placing at the disposal of the constant-flow pump 1 the excess of power W of the motor 3, before starting to reduce the power available for driving the variable-flow pump 2. 1f:

M W' E (7) PC being the delivery pressure of the constant-flow pump 1 corresponding to the excess power W It is only when P becomes greater than P that the driving power to the pump 2 must be reduced. The graph in FIG. 2 makes clear the sharing of power which has just been indicated. lt isa question of performing the subtraction: V

vF r c E) which is deduced otherwise from comparison of (5) and (7).

The regulator 16 in principle knows nothing of the functioning of the constant-flow pump 1. For the regulation of the variable-flow pump 2 to take into account the power already taken off first from the total power W of the motor 3 for the driving of the pump 1, the regulator 16 has to be connected by the pipe 50 to the valve 29. One has to pass from the operation represented by the curve C to that represented by the curve C,. On this curve C, one has:

w VI=PVXQVI VF H QV (11) according as one accepts reducing the flow from Qv to O or reducing the pressure from P to P of the variable-flow pump 2, the pressure Py or the flow Q respectively remaining constant.

.By means of the piston 45 the regulator 16 can take into account the power (W -W to be subtracted and which corresponds in fact in a simple manner for the pump 2 in a reduction A P in its delivery pressure, the flow Q remaining constant:

A W,=P XQ (14) with PI;PYPH (15) A W being the power having to be subtracted from W in order to enable effective driving of the two pumps 1 and 2 by the motor 3. By comparing and combining (14), (13), (8), (2) and (1) one obtains successively:

The valve 29 enables A P to be obtained proportional to A P the coefficient of proportionality being constant for a given feeding device. This pressure A P acts on the piston 45 and provides a force which is added to the force from the pressure P acting on the piston 19. The system of regulation in that case functions as if the delivery pressure from the variable-flow pump 2 were equal to P and corresponded with the curve C(Wy) whereas in fact the pump 2 functions in accordance with the curve C (W That is, the pressure of the fluid which enters through the inlet aperture 40 is equal to the difference (P -P 13) between the delivery pressure P of the constant-flow pump and the calibration pressure of the valve 52, which is exactly equal to P E. The pressure of the fluid which leaves the valve 29 through the outlet orifice 41 is deduced from the pressure of the inlet fluid except for the load loss. This pressure is therefore also in turn proportional to the difference (P P On the other hand, the constriction constituted by the length L, of the groove 43 being of linear type, the pressure obtained in the channel 42 and consequently at the level of the outlet orifice 41 is proportional to the length las has already been observed. The latter is obviously proportional to the pressure of the fluid contained in the chamber 34, that is to say, still to the delivery pressure P]; of the variable-flow pump 2.

Consequently, the pressure of the fluid which leavs the valve 29 through the aperture 41 is equal to:

A H r m: )XPVXK (17) K being a constant proportionality coefficient, the value of which depends in particular upon the stiffness of the spring 37.

If this pressure A P acted directly upon the piston 19 of the regulator 16 it would act upon the rod 18, taking into consideration the springs 25, in the same way as the pressure P of the fluid contained in the chamber 21. It may be necessary to make it act upon piston 45 distinct from the piston 19. If in that case S and S are the respective sections of the pistons 19 and.45, the pressure of the fluid contained in the pipe 5 0 which is to act upon the piston 45 should have the value:

A l A H 45/ 19) (b 1 By replacing A P in (18) by the value quoted in,( 16) and A P by the value indicated in (17) one obtains:

The choice of the stiffness of the spring 37, section of the bore 33, and sections of the pistons 19 and 45, Q and W being imposed functional values, enable the equation (19) to be very easily satisfied.

So doing, the power (W -W is effectively subtracted from W which becomes W equation (9) being realized, whilst the power W necessary for driving the constant-flow pump 1 is realized by the sum on the one hand of W the excess power defined by the equation (7') derived from (7), and on the other hand of the power (W -W previously subtracted from the driving of the variable-flow pump 2.

Naturally, of course, the power W of the motor 3 is found to be equal to the sum of the powers necessary for driving the pumps 1 and 2:

The equation (21) is in fact nothing else but (5) rewritten in another form.

There is thus described a device which is simple in construction which enables its manufacture at not very high cost.

It will be appreciated that the above described device may be modified without departing from the scope of the invention.

Thus, of course, the regulation can be effected in the case of a number of variable-flow pumps. In this configuration the fluid in the pipe 36 has a pressure equal, not to the delivery pressure from one of the variable-flow pumps, but to the arithmetic mean of the delivery pressures of all the variable-flow pumps. The outlet pressure from the valve 29 (aperture 41) may in that case be employed for shedding the load from either one or a number of the variable-flow pumps.

It will be appreciated that the presence of the calibrated valve 52 is only really interesting when:

WM t

That is, if W =W it is necessary, from the start of the regulation, to reduce W But it must likewise be observed that even if (6) is realized, the calibrated valve 52 is not indispensable. Nevertheless, if the calibrated valve 52 is not provided the excess power W and the pressure P which corresponds to it will be considered as being equal to zero in the various equations so that from the very start of driving the constant-flow pump 1 its driving power W will be wholly subtracted from the driving power W to the variable-flow pump 2. That can still be imagined by reason of simplification when W is relatively low and moreover (W W is likewise low.

Purely by way of example, the load circuit 14 may consist of the circuit for translation of the hydraulic shovel, the load circuit 28 in that case consisting of the circuit for feeding the boom and the bucket of the shovel and being considered as priority during work on the site of public works.

Finally, it will be observed again that it is possible in order to increase the properties of regulation of the complete device, to arrange in one of the two pipes 50 or 51 a supplementary constriction which is variable and manually adjustable.

What is claimed is: l. A device for feeding fluid under pressure to at least two load circuits, comprising:

two groups of pump means for feeding fluid to a respective one of said load circuits and each including a pump, a driving shaft and a delivery pipe, one of said groups of pump means being constant-flow and the other of said groups being variable-flow,

flow control means associated with said variable-flow group,

driving motor means having a single output shaft to which are coupled the driving shafts of said pumps, power regulator means including a body and an ele ment movable with respect to the body and which is coupled between the flow control means and the body of said variable-flow group of pump means, said regulator including ram means interposed between said body and said movable element of said regulator and comprising an inlet chamber, pipe means connecting the delivery pipe from said constant-flow group of pump means to said inlet chamber, and

a valve arranged in said connecting pipe means and comprising a body, a slide movably mounted in said body, an inlet connected to said delivery pipe by said connecting pipe means, two outlets of which a first outlet is connected to a fluid tank and the second outlet is connected to said inlet chamber of said ram means by said connecting pipe means, a fluid connection for control of the position of said slide, said fluid connection being connected to the delivery pipe of said variable-flow group of pump means, and a passage between said body and said slide of said valve at least one of the dimensions of which varies as a function of the position of the said slide in said body, said inlet, said first outlet and said second outlet being in permanent communications with said passage, said second outlet communicating with said passsge at a region intermediate communication of said inlet and said first outlet with said passage, and the portion of said passage lying between the regions of communication of said inlet and said second outlet with said passage forming a variable fluid constriction.

2. A feeding device as claimed in claim 1, including a calibrated valve arranged in said connecting pipe means between said valve and the connection of said connecting pipe means to said delivery pipe of said constant-flow group of pump means, to be piloted by the pressure of fluid in said delivery pipe.

3. A feeding device as claimed in claim 1, wherein said slide is mounted to slide in said body of said valve and is bored to receive an elongate control fluid delivery member in sealing engagement therewith, said slide being movable relatively to said elongate member, and being subjected to the effect of the pressure of the control fluid and the opposing action of a return member coupled between the slide and said body of said valve.

4. A feeding device as claimed in claim 1, wherein said passage is defined by a groove in the outer face of said slide of said valve and a channel in said slide and connecting said groove with a recess in said body of said valve which is connected to said second outlet from said valve, said groove being permanently connected to said inlet and said first outlet, the value of said variable constriction being proportional to the distance separating the regions of communication of said first and second outlets with the passage.

5. A feeding device as claimed in claim 1, wherein the power regulator includes second ram means interposed between its body and movable element and comprises an inlet chamber connected to said delivery pipe of said variable-flow group of pumps, a return member being interposed between said body and said movable element of said regulator and having an effect opposed to that of fluid when contained in the inlet chamber of the first ram means. 

1. A device for feeding fluid under pressure to at least two load circuits, comprising: two groups of pump means for feeding fluid to a respective one of said load circuits and each including a pump, a driving shaft and a delivery pipe, one of said groups of pump means being constant-flow and the other of said groups being variable-flow, flow control means associated with said variable-flow group, driving motor means having a single output shaft to which are coupled the driving shafts of said pumps, power regulatoR means including a body and an element movable with respect to the body and which is coupled between the flow control means and the body of said variable-flow group of pump means, said regulator including ram means interposed between said body and said movable element of said regulator and comprising an inlet chamber, pipe means connecting the delivery pipe from said constant-flow group of pump means to said inlet chamber, and a valve arranged in said connecting pipe means and comprising a body, a slide movably mounted in said body, an inlet connected to said delivery pipe by said connecting pipe means, two outlets of which a first outlet is connected to a fluid tank and the second outlet is connected to said inlet chamber of said ram means by said connecting pipe means, a fluid connection for control of the position of said slide, said fluid connection being connected to the delivery pipe of said variable-flow group of pump means, and a passage between said body and said slide of said valve at least one of the dimensions of which varies as a function of the position of the said slide in said body, said inlet, said first outlet and said second outlet being in permanent communications with said passage, said second outlet communicating with said passsge at a region intermediate communication of said inlet and said first outlet with said passage, and the portion of said passage lying between the regions of communication of said inlet and said second outlet with said passage forming a variable fluid constriction.
 2. A feeding device as claimed in claim 1, including a calibrated valve arranged in said connecting pipe means between said valve and the connection of said connecting pipe means to said delivery pipe of said constant-flow group of pump means, to be piloted by the pressure of fluid in said delivery pipe.
 3. A feeding device as claimed in claim 1, wherein said slide is mounted to slide in said body of said valve and is bored to receive an elongate control fluid delivery member in sealing engagement therewith, said slide being movable relatively to said elongate member, and being subjected to the effect of the pressure of the control fluid and the opposing action of a return member coupled between the slide and said body of said valve.
 4. A feeding device as claimed in claim 1, wherein said passage is defined by a groove in the outer face of said slide of said valve and a channel in said slide and connecting said groove with a recess in said body of said valve which is connected to said second outlet from said valve, said groove being permanently connected to said inlet and said first outlet, the value of said variable constriction being proportional to the distance separating the regions of communication of said first and second outlets with the passage.
 5. A feeding device as claimed in claim 1, wherein the power regulator includes second ram means interposed between its body and movable element and comprises an inlet chamber connected to said delivery pipe of said variable-flow group of pumps, a return member being interposed between said body and said movable element of said regulator and having an effect opposed to that of fluid when contained in the inlet chamber of the first ram means. 